[PATCH v3 3/3] net: qcom/emac: Prevent device_find_child() from modifying caller's match data

[Zijun Hu <zijun_hu@icloud.com>]

From: Zijun Hu <quic_zijuhu@quicinc.com>

To prepare for constifying the following old driver core API:

struct device *device_find_child(struct device *dev, void *data,
		int (*match)(struct device *dev, void *data));
to new:
struct device *device_find_child(struct device *dev, const void *data,
		int (*match)(struct device *dev, const void *data));

The new API does not allow its match function (*match)() to modify
caller's match data @*data, but emac_sgmii_acpi_match() as the old
API's match function indeed modifies relevant match data, so it is not
suitable for the new API any more, solved by using device_for_each_child()
to implement relevant functions.

Signed-off-by: Zijun Hu <quic_zijuhu@quicinc.com>
---
 drivers/net/ethernet/qualcomm/emac/emac-sgmii.c | 22 +++++++++++++++++-----
 1 file changed, 17 insertions(+), 5 deletions(-)

diff --git a/drivers/net/ethernet/qualcomm/emac/emac-sgmii.c b/drivers/net/ethernet/qualcomm/emac/emac-sgmii.c
index e4bc18009d08..29392c63d115 100644
--- a/drivers/net/ethernet/qualcomm/emac/emac-sgmii.c
+++ b/drivers/net/ethernet/qualcomm/emac/emac-sgmii.c
@@ -293,6 +293,11 @@ static struct sgmii_ops qdf2400_ops = {
 };
 #endif
 
+struct emac_match_data {
+	struct sgmii_ops **sgmii_ops;
+	struct device *target_device;
+};
+
 static int emac_sgmii_acpi_match(struct device *dev, void *data)
 {
 #ifdef CONFIG_ACPI
@@ -303,7 +308,7 @@ static int emac_sgmii_acpi_match(struct device *dev, void *data)
 		{}
 	};
 	const struct acpi_device_id *id = acpi_match_device(match_table, dev);
-	struct sgmii_ops **ops = data;
+	struct emac_match_data *match_data = data;
 
 	if (id) {
 		acpi_handle handle = ACPI_HANDLE(dev);
@@ -324,10 +329,12 @@ static int emac_sgmii_acpi_match(struct device *dev, void *data)
 
 		switch (hrv) {
 		case 1:
-			*ops = &qdf2432_ops;
+			*match_data->sgmii_ops = &qdf2432_ops;
+			match_data->target_device = get_device(dev);
 			return 1;
 		case 2:
-			*ops = &qdf2400_ops;
+			*match_data->sgmii_ops = &qdf2400_ops;
+			match_data->target_device = get_device(dev);
 			return 1;
 		}
 	}
@@ -356,10 +363,15 @@ int emac_sgmii_config(struct platform_device *pdev, struct emac_adapter *adpt)
 	int ret;
 
 	if (has_acpi_companion(&pdev->dev)) {
+		struct emac_match_data match_data = {
+			.sgmii_ops = &phy->sgmii_ops,
+			.target_device = NULL,
+		};
 		struct device *dev;
 
-		dev = device_find_child(&pdev->dev, &phy->sgmii_ops,
-					emac_sgmii_acpi_match);
+		device_for_each_child(&pdev->dev, &match_data, emac_sgmii_acpi_match);
+		/* Need to put_device(@dev) after use */
+		dev = match_data.target_device;
 
 		if (!dev) {
 			dev_warn(&pdev->dev, "cannot find internal phy node\n");

-- 
2.34.1